The patent laws require that the claims of a patent (which define the boundaries of what the patent owner can protect) “particularly point out and distinctly claim the subject matter … of the invention.”  35 U.S.C. §112, ¶2.  This requirement is referred to as “definiteness.”  A patent that fails to satisfy this requirement may be found to be invalid for indefiniteness.

The purpose of the definiteness requirement is to provide the public with notice of what the patent owner owns, and what would be an infringement of the patent.  Thus, the definiteness requirement serves to encourage innovation by providing certainty as to what the patent protects.

This year, the United States Supreme Court vacated a Federal Circuit Court of Appeals decision on the grounds that the Federal Circuit’s test for indefiniteness was not precise enough and would result in confusion in the district courts.  The case is Nautilus, Inc. v. Biosig Instruments, Inc., 189 L.Ed. 2d 37 (June 2, 2014).

In 2004, the patent owner, Biosig, sued Nautilus for infringement of a patent covering a heart-rate monitor used in exercise.  Biosig’s heart monitor was different from existing heart monitors in that it was more accurate because it did not measure both electrical signals from the user’s heart and from the muscles.  The Biosig heart monitor used two pairs of electrodes, one pair for each hand of the user.  Biosig alleged that Nautilus, who owned the StairMaster brand of exercise machine, used the patented heart monitor in StairMaster machines.

In its claim construction decision, the district court for the Southern District of New York construed the phrase “spaced relationship” between the electrodes.  The district court held that this phrase means “a defined relationship,” but did not include any reference to the distance between the two pairs of electrodes.

Nautilus moved for summary judgment on the grounds that the “spaced relationship” was indefinite and rendered the patent invalid.  The district court granted the motion on the grounds that the phrase did not specify the distance between the pairs of electrodes or state how that distance should be calculated.

On appeal, the Federal Circuit reversed and remanded the case.  The court held that the test for indefiniteness is met “‘only when [the claim] is not amenable to construction or insolubly ambiguous.’”  Nautilus, supra, at 46, quoting the Federal Circuit’s decision, 715 F.3d 891, 898 (2013).  The Federal Circuit found that Biosig’s patent claims were not indefinite under this test.

On appeal to the Supreme Court, Biosig argued that a claim is definite enough to satisfy section 112 as long as it “provides reasonable notice of the scope of the claimed invention.”  Id. at 47.  Nautilus contented that a claim is indefinite if it is “ambiguous, such that readers could reasonably interpret the claim’s scope differently.”  Id.

In analyzing the issue, the Court explained that section 112 requires a balance.  There will always be some uncertainty, as “the price of ensuring the appropriate incentives for innovation.”  Id. at 47.  However, a claim must also:

“… be precise enough to afford clear notice of what is claimed, thereby ‘appris[ing] the public of what is still open to them.’  [Citations omitted.]  Otherwise there would be ‘[a] zone of uncertainty which enterprise and experimentation may enter only at the risk of infringement claims.’”

Id. at 48.

According to the Court, at 48, section 112 requires that:

“… a patent’s claims, viewed in light of the specification and prosecution history, inform those skilled in the art about the scope of the invention with reasonable certainty.”

The Court noted that patent applicants have an incentive to be as vague as possible in drafting claims.  Therefore, the Court found that the incentive must be reversed, and the burden should be on the applicant to draft clear and unambiguous claims.  Id. at 48.

The Court held that the Federal Circuit’s test of “amenable to construction” and “insolubly ambiguous” was too imprecise, and would cause confusion in the lower courts.  The Court stated, at 49:

“It cannot be sufficient that a court can ascribe some meaning to a patent’s claims; the definiteness inquiry trains on the understanding of a skilled artisan at the time of the patent application, not that of a court viewing matters post hoc.  To tolerate imprecision just short of that rendering a claim ‘insolubly ambiguous’ would diminish the definiteness requirement’s public-notice function and foster the innovation-discouraging ‘zone of uncertainty,’ against which this Court has warned.”

The Court did not address whether Biosig’s patent satisfied section 112’s definiteness requirement or was indefinite and therefore invalid, remanding the case to the Federal Circuit for that determination.